CYTOLOGICAL AND MORPHOLOGICAL DIVERSITY OF NATIVE APOMICTIC BUFFELGRASS, PENNISETUM-CILIARE (L) LINK

Diverse native morphotypes of apomictic buffelgrass (Pennisetum ciliare [L.] Link [Cenchrus ciliaris L.] were investigated cytologically to determine the sources of variation and to establish relationships among widely different natural accessions. The primary objectives were to determine mode of reproduction of accessions and hybrid progenies through embryo sac studies and to assess the potential of the material for use as germplasm in a breeding program. Although most native buffelgrass ecotypes are obligate apomicts, reproductive studies showed evidence for sexual reproduction (facultative apomixis) in each of five accessions chosen for a hybridization study. A fully differentiated single sexual embryo sac was observed in 7% of the ovules from two accessions, each of which also had one facultative ovule. Cytological studies on five of the most diverse types and their F1 hybrids with a sexual buffelgrass clone (B-1s) showed very similar chromosome pairing relationships at metaphase I of parents and their progenies. These results demonstrate a close relationship between types and indicate that they represent a primary gene pool for breeding purposes. The extreme morphological diversity present in the types is explained by the limited sexual reproduction. Highly apomictic divergent morphotypes could colonize large areas and easily be mistaken for different species.